The present invention relates to a method of heating a band for a cathode ray tube (CRT) and an apparatus therefor, and more particularly, to a method of heating an implosion-proof band in a process of banding the CRT and an apparatus therefor.
The banding process in the fabrication of a CRT involves a process of attaching an implosion-proof band having a predetermined tension on the outer surface of the CRT, thereby preventing an implosion due to cracks in the CRT and improving the effectiveness of the implosion prevention. Generally, a spherical vessel among various vacuum vessels is the most suitable for preventing implosion. However, in the case of the CRT which is not spherical, the banding process is additionally required for preventing implosion. That is, since the outer surface of the CRT has a tensile stress and the inner surface thereof has a compressive stress; the effectiveness of implosion prevention can be increased by the banding process in which a compressive stress corresponding to the tensile stress is applied. In general, a weld banding method is widely used which is comprised of a heating step and a welding step. Here, the heating step is performed to increase tension by thermally expanding the implosion-proof band using an additional heater. The thermally-expanded implosion-proof band is attached to the outer surface of the CRT and then cooled so that the implosion-proof band is shrunk and combined with the outer surface of the CRT.
Conventionally, the implosion-proof band is expanded by heating the implosion-proof band using gas or electricity. Here, the gas heating method is used to heat the implosion-proof band using an apparatus for generating heat, for example, a gas burner. Also, the electricity conduction method is used to apply a low voltage and high current to the implosion-proof band and to heat the band with heat generated by the resistance generated when the implosion-proof band contacts two voltage terminals. However, in the conventional heating method, since heat cannot be consistently and continuously applied to the implosion-proof band due to its characteristics, the following problems are generated. First, since the implosion-proof band does not uniformly expand, the effectiveness of the implosion prevention relatively degrades. Second, since the implosion-proof band does not completely expand, it does not properly insert into the outer wall of the CRT in the next welding step. Third, oxidation of the implosion-proof band is highly probable due to the deterioration of the surface of the implosion-proof band.